Multiple-modulation system



April 7, 1931. L. ESPENSCHIED MULTIPLE MODULATION SYSTEM Filed March so, 1929 Lator P Eizrmwuc Producer 25 5 lNVENTOR I LEIs e/mscizzew BY Patented Apr. 193 1 UNITED STATES PATENT ounce LLOYD ESPENSCHIED, or .KEW GARDENs'NEW Yon-K, essIGnoR 510' AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION or new YORK MULTIPLE-MODULATION SYSTEM Application filed March 30, 1923. Serial N'o. 351,222.

mitting and the receiving portions of such;

systems. The arrangements .of the invention have the advantage in multiple demodulation receivers of making it necessary to adjust the frequency ofonly one oscillator in tuning the receiving set. The carrier supplies for the various demodulation stages are automatically kept in proper frequency alignment by selecting harmonics of the single oscillator, which appear in the outputs of the various demodulators and feeding them into preced 2 ing demodulator stages as the vbeating freq ya Multiple detection systems'in the past, have consisted of a number of detectors or demodulators with their associated oscillators, separated by amplifiers and filters. The object'of such a system has been to change thefrequency of the input potential from high values, down to a range where it may be satisfactorily amplified. The fact that a multiplicity of oscillators must be used in such a system hasadded considerably to its complexity of design and adjustment because the frequencies of the demodulator oscillators must be so chosen that'unwanted frequencies, dueto-their combinations or combinations of their harmonics, do not appear in the audio-frequency output, On the assumption that a suitable combination of frequencies has been found, it is necessary to continually adjust a number of oscillators to compensate for any frequency'instability.

, With the arrangements'of the invention, if the radio signals tobe received are, for example, of very high frequency and of the type known as suppressed carrier, apparatus comprising a plurality of stages of demodulation such, for example, as four might be utilized. A single, oscillatorjwould be=provided. This would be used' to supply the pseudo-carrier frequency corresponding v to of the supplied carrier frequency P. A suitable band filter is used to select the Nth har monic ofithis series, which is applied as a carrier for the preceding demodulator. In this third demodulator, there is obtained a side-band output and, as above, there is selected the Kth harmonic of the carrier supplied to this stage. The above process may be continued asfar as design considerations require. q

The advantages of the method and arrangements of the invention as outlined above, are as follows: Since, only one oscillator is used, economy is attained through the elimination, of a multiplicity of oscillators. Simplicity of adjustment follows from the fact that there is only one oscillator to be corrected in themaintenance of constant frequency. Since all the supplied carriers are harmonics of a single frequency, they can not vary in respect to each other and hence, constancy of frequency alignment is obtained. Since all the supplied carriers are harmonics of a single frequency, they can not beat together at audible frequency. By elimination or addition of demodulation stages, the same receiver may be used for reception over a very wide band of frequencies.

Qther features and advantages of the invention will appear more fully from the detailed description thereof hereinafter given.

The invention may be more fully understood from the following ClGSCI'iPtiOIitO- gether with the-accompanying drawing in theFigures 1, 2 and 3 of which the invention is illustrated. F 1 shows a schematic arrangement of the invention, as applied to a receiving set. Fig. 2 shows in detail a portion of the arrangements of Fig. 1. Fig. 3

is a modification of the arrangements of Fig. 1. Similar. reference characters have been used to denote like parts in all of thefigures.

In Fig. 1 there is shown schematically, a

.portion'of a receiving station utilizing the principles of the invention. In this arrangeto translate the incoming high frequency signal q down to a lower frequency S. Accordingly, the demodulators D D D and D are illustrated. These demodulators might be of the well known balanced duplex type. The demodulator D. is shown in more detail in Fig. 2. Interconnecting these demodulators, are the filters F F F and F 4 and the amplifiers A A and A A single oscillator is used to supply current of a frequency P to the demodulator D This will be of a frequency corresponding to the carrier utilized at the transmitting station. In a carrier suppression type system, this carrier would have been suppressed at the sending station. By use of suitable branches in the balanced demodulator D as shown more fully in Fig. 2, there is obtained the output side-band S and a series of harmonics of the supplied carrier frequency P. A suitable band filter F is utilized to select the Nth harmonic of the carrier P. This frequency NP is then applied as a beating frequency to the preceding demodulator which is D By use of a suitable branch circuit and the filter F, there is obtained from demodulator D the Kth harmonic of the series from frequency P. This is then applied as a beating frequency to the neXt preceding demodulator D By use of a suitable branch circuit and the filter F, there is obtained from demodulator D the Mth harmonic of the series from frequency P. This is applied to the demodulator D as a carrier for modulation with the incoming high frequency 9.

7 To more completely illustrate the operation of the arrangements of the invention as shown in the receiving set of Fig. 1, let it be assumed that the incoming frequency 9 is of the order of 50,000 KC, or 6 meters. Let it be assumed that the amplifiers A A and A and the filters F F and F are designed to pass frequencies of 5,000 KG, 500 KQ and SO'KC, respectively. The frequencies in the various portions of the circuit Wlll then be as follows MKNP=45,000 KC KNP= 4,500 KC NP= 450 KC P= 50 KC Therefore, M, K and N, which are integral multiples of P, will have the following In other words, it is assumed that we are receiving single side-band transmission and are supplying from the local oscillator a carrier frequency P of 50 KG in obtaining voice frequencies S from demodulator D Demodulator D accordingly, is supplied with a carrier of 50 KC and in turn, supplies to demodulator D a carrier of 450 KC which is the ninth harmonic of its oscillator of frequency P. The demodulator D being suplied with its incoming slgnal frequency of 500 K0 and with the 450 KC earner, feeds to demodulator D the tenth harmonic of 450 KC, or a carrier of 4,500 KC. The demodulator D being supplied with its incoming signal frequency of 5,000 KC, and with the carrier of 4,500 KC, feeds to demodulator D the tenth harmonic of 4,500 KC, or a carrier of 45,000 KC. In other words, the carrier supplied to demodulator D will be 900 times the oscillator frequency P. As a result of these stages of frequency transformation, there is obtained a zero frequency output at S when a frequency equal to the untransmitted carrier, or 50,000 KC, is ap plied at the input of the set. A frequency of 50,000,045 cycles at the input would give 45 cycles at the output. Although the above specific illustration has been chosen as applied to single side-band reception, it is pointed out that the method and arrangements of the invention may equally well be applied to other types of systems, such as those in which the carrier is transmitted, by utilizing receiving apparatus suitable for type of system employed.

The method and arrangements of the invention are applicable to a. transmitting station as well as to a receiving station. When the arrangements of the invention are utilized for transmitting, arrangement similar to those of Fig. 1 may be utilized to step up the frequency from the voice range to the frequency to be radiated at the antenna by a suitable reversal of the path of the applied signal through the apparatus and by making the demodulators act as modulators.

In Fig. 3 there is shown a modification of the arrangements of the invention as applied to a radio receiving system. Similar refere'nce characters have been utilized for parts identical with those of the arrangements of Fig. 1. The transmission line will include the demodulators D D D and D.,. As before, these demodulators will be interlinked by the filters F F F F and F and the amplifiers A A and A The demodulator D will be supplied with a carrier frequency P from the single oscillator shown. The oscillator output will'also be connected to a harmonic producer HP Connected to the output of harmonic producer HP will be a branch circuit including the filter F which will select the Nth harmonic of the carrier frequency P and apply it as a carrier to the demodulator D Connected to the output of harmonic producer HP will be a branch circuit including the filter F which will'select the Kth harmonic of the series from P and will apply it as a carrier to the demodulator D Included in the output circuit of harmonic producers HP is a filter F which will select the Mth harmonic of the series from P and apply it as a carrier to demodulator D As further operation of the arrangements is substantially similar to that of Fig. 1, no further description thereof will be given.

While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many other and Widely varied forms without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. The method of effecting a translation of signals from a certain position in the frequency spectrum to certain other positions in the frequency spectrum which comprises subjecting said signals to a plurality of stages of modulation, supplying a fundamental frequency as a carrier for one of said stages of modulation, selecting a harmonic of, said fundamental frequency from the output of said stage as the carrier for an adjacent stage of modulation, and successively selecting from the output of such adjacent stage of modulation the carrier frequency for the next adjacent stage of modulation.

2. The method of effecting a translation of signals from a certain position in the frequency spectrum to certain other positions in the frequency spectrum which comprises subjecting said signals to successive stages of modulation and utilizing a product of each stage of modulation as the carrier frequency for the next adjacent stage of modulation. 3. The method of receiving high frequency signals which comprises subjecting said signals to successive stages of demodulation and utilizing a product of each demodulation stage to control the preceding stage of demodulation.

4. The method of receiving high frequency signals which comprises subjecting said signals to successive stages of demodulation and utilizing a product of the demodulation in the last successivestage to control the preceding stages of demodulation.

5. The method of receiving high frequency signals which comprises subjecting said signals to successive stages of demodulation,

providing a fundamental carrier frequency for the last successive stage of demodulation, selecting from the product of said last stage of demodulation a harmonic of said fundamental carrier frequency and utilizing said selected harmonic frequency to control the nextpreceding stage of demodulation. I

6. A high frequency translating device comprising a circuit interconnecting a plurality of demodulators, an oscillator for supplying a carrier frequency for one of said demodulators, a branch circuit connected to the output of said demodulator, means in said branch circuit for selecting a harmonic of said carrier frequency, and means for connecting said branch c1rcu1t toa preceding one of said demodulators whereby said selectt quency signals by a plurality of steps, an

oscillator for supplying a carrier frequency for one of said demodulators, means for selecting from the output of said demodulator a harmonic of said carrier frequency, means to supply said harmonic as the carrier frequency for the next preceding demodulator, means to derive from the output of the next preceding demodulator a harmonic.

of the carrier frequency thereof, and means 7 to supply said harmonic as the carrier frequency for still another preceding demodulator.

In testimony whereof, I have signed my name to this specification this 27th day of March, 1929.

LLOYD ESPENSCHIED. 

